1. Field of the Invention
The present invention relates to a solar cell module having a photovoltaic element provided therein and which has a porous incombustible member having a structural strength and a back face member provided in this order on a back face side of said photovoltaic element, a solar cell-bearing roof in which said solar cell module is used, and a solar cell power generation system in which said solar cell module is used.
2. Related Background Art
In recent years, societal consciousness of the energy resources and the problems relating to the environment has been increasing all over the world. Particularly, apprehensions for possible exhaustion of petroleum and the like and also for heating of the earth because of the so-called greenhouse effect due to an increase of atmospheric CO2 have been seriously discussing.
Under such circumstance, there is an increased societal demand for early realization of a power generation system capable of providing clean energy without causing CO2 buildup as in the case of thermal power generation.
As such power generation system, public attention has been focused on a solar cell power generation system in which a solar cell module comprising a photovoltaic element (or a solar cell) provided therein is used, for the reason that it generates clean electric energy (power) by way of directly converting sunlight into said electric energy, without causing environmental destruction, where said sunlight Is evenly accessible at any place in the world.
As typical examples of such photovoltaic element used in the solar cell power generation system, there are known crystalline silicon series photovoltaic elements (solar cells) in which crystalline silicon semiconductor materials are used and amorphous silicon series photovoltaic elements (solar cells) in which amorphous silicon semiconductor materials are used.
Aforesaid solar cell module typically comprises at least a photovoltaic element group comprising a plurality of such photovoltaic elements electrically serialized which is sealed by a sealing resin and a surface protective member comprising a glass plate or a transparent resin film which is provided on the light receiving face side of the photovoltaic element group sealed by the sealing resin As the sealing resin, an organic polymer resin such as EVA (ethylene-vinyl acetate copolymer) or the like is generally used.
Such solar cell module is generally used by installing it on a desired installation place such as a roof of a building which is evenly accessible to sunlight, in order to obtain an electric power. The solar cell module used in this way is configured in the form of a roof-integral type solar cell module, an on-roof installation type solar cell module, an on-trestle installation type solar cell module, or the like.
In the case where the installation place is of a large area such as a roof of a building, it generally takes such a manner that a plurality of given solar cell modules are arranged thereon while being electrically connected with each other to establish a solar cell module array thereon.
Now, in the case where a plurality of solar cell modules having such configuration as above described are installed on a roof of a building in such way as above described, there have been pointed out that such problems as will be described below are liable to entail.
That is, Japanese Unexamined Patent Publication No. 86066/1996 (hereinafter referred to as document 1) describes that in the case where a plurality of solar cell panels comprising a tempered glass plate, a filler resin (comprising EVA), a photovoltaic element (a photovoltaic element group), a filler resin (comprising EVA) and a layered member (comprising a PVF (polyvinyl fluoride) film/an Al foil/a PVF film) stacked in this order from the light receiving face side are installed on a roof of a building in such way as above described, when a fire is occurred near the building, the fire is spread to the building, and the solar cell panels situated on the eaves side of the roof thereof are exposed to flame or heat radiated from the spreading fire, there is a fear that the glass plates of the solar cell panels involved are broken due to the flame or heat, and their filler resins comprising EVA are heat-fused or burned to flow to the outside.
Japanese Unexamined Patent Publication No. 148614/1997 (hereinafter referred to as document 2) describes that in the case where a plurality of solar cell modules comprising a tempered glass plate, a filler resin (comprising EVA), a photovoltaic element (a photovoltaic element group), a filler resin (comprising EVA) and a layered member(comprising a PVF film/an Al foil/a PVF film) stacked in this order from the light receiving face side are installed on a roof of a building in such way as above described, when a fire is occurred near the building and the fire Is spread to the building, there Is a fear that for the solar cell modules which are exposed to heat radiated from or flame of the spreading fire, their glass plates as the front side protective member are broken due to the heat or flame, and the broken glass plates are scattered or their filler resins comprising EVA are heat-fused to flow to the outside to cause firing at the roof bed.
Those problems mentioned in documents 1 and 2 and other problems which will inferred therefrom can be summarized as follows.
For the solar cell modules having such configuration as above described which are installed on the roof of the building, when a fire is occurred near the building and the fire is spread to the building, (i) their glass plates are broken due to heat radiated from or flame of the spreading wire, where the broken glass plates are scattered; (ii) when the glass plates are broken, the filler resins comprising EVA are heat-fused due to the heat to burn or flow to the outside; (iii) when the heat-fused EVA are flown to reach the roof bed, the roof bed will catch fire and burn; (iv) when the filler resins comprising EVA are heat-fused and burned, not only the scattered glass plate particles but also the photovoltaic elements which are sealed by the filler resins are dropped out to the roof bed.
Now, Japanese Unexamined Patent Publication No. 64396/1997 (hereinafter referred to as document 3) discloses a solar cell module which comprises a body comprising a solar cell having an electrically conductive transparent film bonded to the surf ace thereof and an electrically conductive film bonded to the back face thereof provided between a transparent glass plate and an incombustible back member, and a sealing member provided so as to waterproof a peripheral portion of said body. However, in the production of the solar cell module described in document 3, after the solar cell is produced, the incombustible back member is bonded by means of an adhesive. Thus, there are disadvantages such that the productivity of the solar cell module is inferior and the solar cell module is costly.
Japanese Unexamined Patent Publication No. 69646/1997 (hereinafter referred to as document 4) discloses a solar cell module comprising a solar cell covered by a transparent plate situated on the light receiving face side thereof and a back cover situated on back face side thereof, wherein a mesh body impregnated with an adhesive resin comprising EVA or the like is provided between said solar cell and said transparent plate or/and between said solar cell and said back cover. As said mesh body, there are mentioned a glass fiber unwoven material and the like in document 4. Document 4 describes that because an adhesive resin comprising EVA or the like is impregnated in the mesh body comprising a glass fiber nonwoven material or the like, the adhesive resin is prevented from being dropped and is prevented from being burned in the combustion test, and therefore, the solar cell module is flame resistant or incombustible; and thus, the solar cell module can be used as a roofing material. However, for the solar cell module described in document 4, there is a disadvantage in that when the solar cell module Is installed on a roof and the adhesive resin (EVA) is completely burned out due to a fire occurred in the vicinity of the roof, the solar cell and the like are dropped out onto a sheathing roof board of the roof mainly due to the weight of the solar cell.
Japanese Unexamined Patent Publication No. 302942/1996 (hereinafter referred to as document 5) discloses a structure comprising a solar cell module (a solar cell panel) having a solar cell body provided therein and an incombustible member which is provided on a lower face side of said solar cell module while having an interval between said solar cell body and said incombustible member or without having said interval between said solar cell body and said incombustible member. In the case where incombustible member is provided on the lower face side while having the interval between the solar cell body and the incombustible member, there are disadvantages such that it is necessary to take a procedure that the solar cell module is first produced and thereafter, the incombustible member is provided, and because of this, it takes a lot of time. Document 5 describes that in the case where the incombustible member is provided on the lower face side of the solar cell module so as to have no interval between the solar cell body and the incombustible member, an incombustible member having a plurality of vents is used as the incombustible member. In this case, there are disadvantages such that when the solar cell module is maintained under environmental condition with high temperature over a long period of time, EVA as the filler resin of the solar cell body is liable to ooze out through the vents of the incombustible member, where a sticky material comprising the EVA thus oozed out is occurred. There is also a disadvantage in that due to the vents of the incombustible member, the moisture proof of the solar cell module is liable to deteriorate, where the reliability of the solar cell module is deteriorated Document 5 also describes that a punching metal is used as the incombustible member In this case, there is a disadvantage in that the solar cell module becomes heavy.
Japanese Unexamined Patent Publication No. 227102/1998 (hereinafter referred to as document 6) discloses a solar cell module provided with a wired glass member on the light receiving face side for the purpose of ensuring the safety. For this solar cell module, there is a disadvantage in that because the wired glass member is situated on the light receiving face side of the solar cell module, the light transmittance of the solar cell module is inferior and thus, the photoelectric conversion efficiency of the solar cell module is inferior. Although no glass is scattered when a fire is occurred in the vicinity thereof because of using the wired glass member, the solar cell module has such disadvantages as will be described in the following. That is, cracking is likely to occur at the wired glass member when the fire is occurred, and when the wired glass member is cracked, the fire is liable to invade into the solar cell module through the cracked portions of the wired glass member, where the inside filler resin comprising EVA of the solar cell module is fired and as a result, the photovoltaic element and glass particles caused when the wired glass member is cracked are dropped out.
The present invention is aimed at solving the foregoing problems in the prior art, and providing a solar cell module which satisfies the requirements which will be described below, a solar cell-bearing roof in which said solar cell module is used and a solar cell power generating system in which said solar cell module is used.
The requirements are: (1) even when the solar cell module is burned, the photovoltaic element and surface member thereof are not dropped out onto a sheathing roof board, (2) the solar cell module is ensured with respect to the moisture proof and is highly reliable, (3) the solar cell module is light weight, (4) the solar cell module can be readily produced at a good yield, and (5) the solar cell module is reasonable in price.
Another object of the present invention is to provide a solar cell module having an outermost surface comprising a surface member on the light receiving face side of said solar cell module, a most back face comprising a back face member on the non-light receiving face side of said solar cell module, and a photovoltaic element between said surface member and said back face member, characterized in that said solar cell module has a porous incombustible member having a structural strength between said photovoltaic element and said back face member.
A further object of the present invention is to provide a solar cell-bearing roof comprising a solar cell module fixed to a sheathing roof board, said solar cell module having an outermost surface comprising a surface member on the light receiving face side of said solar cell module, a most back face comprising a back face member on the non-light receiving face side of said solar cell module, and a photovoltaic element between said surface member and said back face member, characterized in that said solar cell module has a porous incombustible member having a structural strength between said photovoltaic element and said back face member.
A further object of the present invention is to provide a solar cell power generation system comprising a solar cell module and a power conversion device electrically connected to said solar cell module, said solar cell module having an outermost surface comprising a surf ace member on the light receiving face side of said solar cell module, a most back face comprising a back face member on the non-light receiving face side of said solar cell module, and a photovoltaic element between said surface member and said back face member, characterized in that said solar cell module has a porous incombustible member having a structural strength between said photovoltaic element and said back face member.